Printing plate matrix



May 26, 1936. T. c. BROWNE PRINTING PLATE MATRIX Filed May 7, 1934 FIG 2Z8 IIIIIIIIIA xmN F l G. 3

FIG. 5

e 0 mw m L M m m m an 6 f wk m5 w Patented May 25, 1936 UNITED STATESPATENT OFFICE PRINTING PLATE MATRIX Theodore C. Browne, Hinsdale, Ill.Application May 7, 1934, Serial.No."I24,273 5 Claims. (01. 41-25) Thisinvention relates to the graphic arts and is particularly directed tothe production of a matrix in which resinous or resin-like rlmningplates may be molded.

In my copending application Serial No. 670,238, filed May 10, 1933, Ishowed how resinous bodies might be cured under considerable pressureandformed into hard, dense masses conforming exactly to the-original shapeof the mold, even if the mold or matrix, as it is commonly called in thegraphic arts, be of a soft, yielding nature.

In an application of Gilbert C. Waters, Serial N0. 724,280, filed May 7,1934, entitled Art of producing printing plates and matrices, a type ortype-containing matrix was disclosed which because it is yieldable,extensible, but self-restoring, always can be removed from the type formno matter how broken the composition or deep the spaces between thetype. It has the further ad} vantages not found in previous matricesthat the full shoulder depth of the type is always reproduced, that nosurfacegrain or structure is introduced, and that shrinkage ispractically eliminated. In fact,the shrinkage is so negligible that sucha matrix retains multi-color registration in 133 line screen workperfectly.

This invention may beconsidered an improvement upon the processes setforth in the above applications and has for its objects to producematrices from mixed forms containing a number of metals, to reduce thepossibility ofchemical damage to expensive half-tone originals; toprevent such chemical action as will render the production of a runningplate in such-a matrix difficult or impossible, and to produce matricesby "closed moulding.

Still other objects and advantages of my invention will be apparent fromthe specification.

The features of novelty which I believe to be characteristic of myinvention are set forth with particularity in the appended claims. Myinvention itself, however, both as to its fundamental principles and. asto its particular embodiments will best be understood by reference tothe specification and accompanying drawing in which Fig. lgivesaperspective view of the form showing the chase modified accordingto my invention.

Fig. 2 is a transverse sectional view through the mould,

3 is a sectional view of one form of matrix,

Fig. 4 is a similar section through an alternative form of matrix, and

Fig. 5 illustrates the method of manufacture, showing the'pressdiagrammatically.

above.

under the name of Duprene.

In the above identified wat ers application the, direction is given toplate the illustrations with some suitable metal such as tin, althoughnickel also is generally suitable.

Although the procedure outlined by Waters 5 .produces consistentlyexcellent results when clean,

fresh type metal makes up the form, it sometimes happens that the resinduplicates made in matrices formed on plated originals or electros, orfrom dirty, much-used type are full of minute blisters. In some cases,both the matrix and the resin running plate are full of small pits.

A chemical investigation of such matrices shows them to be poisoned withcopper. From the exaggerated cases, intentionally produced in the 15experimental work on this invention I have found that copper-rubber, andparticularly the copperrubber-sulphur complexes, of whatever nature theymay be, act like cement, in that they cause the sticking of resinous orresin-like masses to 20 rubber. In some cases, it is impossible toseparate the two without destroying either or both the plate and thematrix when the matrix bears even a very small amount of copper.

' Sticking is not confined to one group of resins 2.5

or even to resins, such very diverse chemical substances asphenol-formaldehyde resins, ureaformaldehyde resins, vinyl resins,chlorinated rubber, chlorinated rubber glucose mixtures, and

the resin-like derivatives known as plioform 30 Successful matrices havebeen made contain- 40 ing, rubber pts., 1, 3, 5 tri-nitro-benzol 2'pts., aniline, 1 pt., and carbon black pts. which were cured 40 minutesin direct contact with copper, without any of the defects noted I muchprefef because of greatly improved mechanical and surfacecharacteristics obtainable, to make matrices having a working face ofpolymerized chloroprene, obtainable commercially tion about thissubstance is available. It is well to point out, however, that its basesubstance bearssuch a resemblance to isoprene, the base substance ofrubber. that great physical resemblance is to be expected.

If the matrix is to be 35 Much informa- 50 Neither does it pick up fromthe copper the ex-' tremely small amounts of poison which are sufiicientto ruin a sulphur-bearing rubber matrix.

As the foregoing applications have pointed out,

lateral deformation of the subsequent moldings or pressings is difiicultto prevent in a rubber or rubber-like matrix, unless the rubber becemented rigidly to a non-extensible member, preferably a thin sheet ofspring brass. v Preferably also, the union of rubber to brass shouldoccur as the matrix is being formed. "Duprene will adhere to rubber whenboth are simultaneously cured and the rubber in turn will adhere to theprepared brass.

Although the open moulding procedure shown in the above identifiedapplications is a great advantage where an enormous number of differentsizes of forms are to be handled as in a jobbing electrotypersestablishment, it is not so certain as is, closed moulding in producinga flat, fully filled matrix. It is possible to secure closed mouldingadvantages in establishments such as book, magazine and catalog printinghouses where a relatively few sizes of forms cover all needs by thefollowing procedure.

The chase, [0, (Fig. 1) is of the ordinary cast iron or welded steelvariety. It is surface ground to some convenient exact thickness and isprovided with four locating holes II, II drilled through the pads at thecorners. The form is composed in the conventional manner except thatwide, accurate type high steel bearers surround the composition and thefurniture I3, is preferably of metal instead of wood. The form is heldin place by the quoins M.

I then provide a nest I5, which is an accurately ground plate of steelhaving a central moulding aperture Hi. It carries four locating pins I1,I! which engage the holes II, II. If the chase I0, is exactly type high(0.918) the shim I8 is unnecessary. Otherwise it is adjusted to bringthe outside bearing for the nest exactly type high. The plunger I9 is aflattened T having a leg or plunger portion 2| which fits within theaperture l6 with about .005" clearance, and a head 22.

In moulding the matrix, the chase Ill and the nest l5 are placed on thelower platen of a press 23, as shown in Fig. 5. A laminated sheet of gumstock having a polymerized chloroprene face and a; backing layer ofrubber gum stock is placed in the aperture l6. On this is placed a thinsheet of spring brass (covered with a cement to promote adhesion to therubber) or a sheet of resin-cement covered resin-impregnated paper.

Then the plunger I 9 is put in place and the press closed against thetop platen 24. Steam is admitted through the conduits 25, 25.

Under ordinary circumstances the inner face 26 of the head 22 engagesthe top surface 21 at the nest IS. The depth at the plunger section 2|controls the thickness at the matrix. If adjustments of thickness arenecessary, they may be compounding. In the example given, the cure iscomplete in ten minutes at eighty pounds steam.

I have found it advantageous to use as the backing layer a rubbercompound which commercially is designated as non-sulphur. Thevulcanizing agent in this case is actually an organic sulphur compoundwhich releases sulphur upon heating. So active, however, is the releasedsulphur that full cure is effected with as little as .017% combinedsulphur.

With such a rubber, extremely thin layers of polymerized chloroprene areall that is necessary (a great advantage, since Duprene is as yet anexpensive substance).

When ordinary sulphur rubber compounds are used (2%,; to 3% sulphur) theexcess sulphur is active and dangerous. Then thicker polymerizedchloroprene is required to insulate and guard the copper from anypossibility of sulphur attack.

The physical similarity of polymerized chloroprene to rubber is close.It is resilient, deformable, self-restoring after deformation, andproduces a matrix which has many of the advantages of rubber. It may bepulled loose from any type form, however complicated, and restoresitself so completely to the original size that registration ofmulticolor fine-screen,-half-tone plates is easily secured.

A considerable number of rubber printing plates are now manufactured bymoulding a thermo-setting resin matrix upon the type surface andthereafter moulding rubber therein. The mould herein described isadapted for the production of such matrices and I have producedextremely accurate and entirely satisfactory thermo-setting matricestherein.

While I have shown and described certain preferred embodiments of myinvention, it will be understood that modifications and changes may bemade without departing from the spirit and scope of my invention as willbe evident to those skilled in the art.

I claim:

1. A matrix for the production of printing plates from molded plasticshaving an impression-bearing face comprising a layer of a sulphur-freeresilient compound capable of relatively large deformation within itselastic limit, an intermediate layer of rubber, and a metallic backvulcanized and united together to form a unitary matrix element.

2. A flexible matrix comprising an impression-bearing face of a sulphurfree chloroprene polymer, an intermediate layer of rubber and areinforcing element which is substantially nonextensible under thepressures to which the matrix is designed to be subjected bondedtogether to form a single unitary structure.

3. A mold liner comprising an impressionbearing surface of acured;fiexible,@ielding sulphur-free resilient substance capable ofrelatively large deformation within its lastic limit, an intermediatelayer of vulcanized soft rubber and a reinforcing member.

4. A non-sticking mold liner for heat reactive resin molding whichcomprises a resilient, yield.- ing, surface of a substantiallysulphur-free chloroprene polymer, a backing layer of rubber, and

reinforcing member having substmtiany zero 5 lateral stretch.

5. A matrix tor molding comprising snimpression-bearing face of asiflphur-tree resilient com-

